Surgical Instrument with Articulating Tool Assembly

ABSTRACT

A surgical stapling instrument including a handle portion, a body portion, an articulating tool assembly and an articulation mechanism is disclosed. The body portion extends distally from the handle portion. The articulation mechanism includes an articulation link for articulating the tool assembly, an articulation knob for rotating an interface member, the articulation link having a slit at a proximal end operatively connected to the interface member, wherein rotational motion of the articulation knob is translated into axial motion of the first and second articulation links thereby articulating the articulating tool assembly.

TECHNICAL FIELD

The present disclosure relates to a surgical instrument having anarticulating tool assembly. More particularly, the present disclosurerelates to a surgical instrument which includes a mechanism foractuating an articulating surgical instrument, e.g., a linear stapler,from a non-articulated position.

BACKGROUND

Surgical instruments which include a tool assembly mounted on a distalend of a body portion of the surgical instrument for articulation arewell known. Typically, such surgical instruments include articulationcontrol mechanisms which allow an operator to remotely articulate thetool assembly in relation to the body portion of a surgical instrumentto allow the operator to more easily access, operate on, and/ormanipulate tissue.

Such articulating tool assemblies have become desirable, especially inthe endoscopic surgical procedures. In an endoscopic surgical procedure,the distal end of a surgical instrument is inserted through smallincisions in the body to access a surgical site. Typically, aappropriately sized cannula, e.g., 5 mm, 10 mm, etc., is insertedthrough the body incision to provide a guide channel for accessing thesurgical site. Because it is desirable to provide small body incisions,i.e., less scarring, reduced trauma to the patient, faster healing time,the tolerances between the surgical instrument and the inner diameter ofthe cannula are small.

Conventional articulating tool tips have a limited range of motionmainly due to mechanical design limitations of actuating mechanisms. Itis desirable to provide an articulating surgical instrument whichincludes an articulation mechanism that would provide a wider range ofmotion for the articulation tip.

SUMMARY

The present disclosure relates to a surgical instrument including ahandle portion, a body portion, an articulating tool assembly and atleast one coupling member. The body portion extends distally from thehandle portion and defines a first longitudinal axis. The articulatingtool assembly defines a second longitudinal axis and is disposed at adistal end of the body portion. The articulating tool assembly ismovable from a first position in which the second longitudinal axis issubstantially aligned with the first longitudinal axis to at least asecond position in which the second longitudinal axis is disposed at anangle to the first longitudinal axis. The articulating tool assemblyalso includes a first articulation link. The articulation mechanismincludes a second articulation link, an articulation knob mountedadjacent the handle portion and mechanically interfacing with anarticulation spindle. The second articulation link is operativelyconnected to the articulation knob at its proximal end and to the firstarticulation link at a distal end, such that rotational motion of thearticulation knob is translated into lateral motion of the first andsecond articulation links thereby articulating the articulating toolassembly.

The present disclosure also relates to a surgical stapling apparatus.The surgical stapling apparatus includes a handle portion including amovable handle, the movable handle being movable through an actuationstroke. The surgical apparatus also includes a body portion extendingdistally from the handle portion and defining a first longitudinal axisand a disposable loading unit configured for releasable engagement witha distal end of the body portion. The disposable loading unit includes aproximal body portion and an articulating tool assembly defining asecond longitudinal axis. The articulating tool assembly is disposedadjacent a distal end of the proximal body portion and is movable from afirst position in which the second longitudinal axis is substantiallyaligned with the first longitudinal axis to at least a second positionin which the second longitudinal axis is disposed at an angle to thefirst longitudinal axis. The apparatus further includes an articulationmechanism including a second articulation link, an articulation knobmounted adjacent the handle portion and mechanically interfacing with anarticulation spindle, the second articulation link having a proximal endoperatively connected to the articulation knob and a distal endpositioned adjacent the distal end of the body portion and operativelyconnected to the first articulation link, wherein rotational motion ofthe articulation knob is translated into lateral motion of the first andsecond articulation links thereby articulating the articulating toolassembly.

The present disclosure also relates to a disposable loading unitconfigured for releasable engagement with a surgical instrument. Thedisposable loading unit includes a body portion, an articulating toolassembly and at least one coupling member.

DESCRIPTION OF THE DRAWINGS

Various embodiments of the presently disclosed surgical instrument aredisclosed herein with reference to the drawings, wherein:

FIG. 1 is a side perspective view from the distal end of one embodimentof the presently disclosed surgical instrument with articulating toolassembly;

FIG. 1A is a side perspective view from the proximal end of a disposableloading unit (DLU) of the surgical instrument shown in FIG. 1 includingthe tool assembly;

FIG. 2 is a side perspective view of the distal end of a mountingassembly and tool assembly, with parts separated, of the DLU of thesurgical instrument shown in FIG. 1;

FIG. 3 is a perspective view of the mounting assembly and the proximalbody portion of the DLU shown in FIG. 1A with parts separated;

FIG. 3A is a side perspective view of a coupling member and retainermember of the surgical instrument shown in FIG. 1;

FIG. 3B is a side perspective view of an upper mounting portion of themounting assembly of the DLU of the surgical instrument shown in FIG. 1;

FIG. 3C is a side perspective view of a lower mounting portion of themounting assembly of the DLU of the surgical instrument shown in FIG. 1;

FIG. 3D is a side perspective view from above of the distal end of theproximal body portion, the mounting assembly and the proximal end of thetool assembly of the DLU of the surgical instrument with the toolassembly in its non-articulated position;

FIG. 3E is a side perspective view from above of the distal end of theproximal body portion, the mounting assembly and the proximal end of thetool assembly shown in FIG. 3D with the tool assembly moving to anarticulated position;

FIG. 3F is a side perspective view from below of the distal end of theproximal body portion, the mounting assembly and the proximal end of thetool assembly of the DLU of the surgical instrument with the toolassembly in its non-articulated position;

FIG. 3G is a side perspective view from below of the distal end of theproximal body portion, the mounting assembly and the proximal end of thetool assembly shown in FIG. 3F with the tool assembly moving to anarticulated position;

FIG. 4 is a side cross-sectional view of the tool assembly of the DLUshown in FIG. 1A;

FIG. 5 is a side perspective view of an articulation mechanism of thesurgical instrument shown in FIG. 1 according to the present disclosure;

FIG. 6 is a perspective internal view of the articulation mechanism ofFIG. 5 according to the present disclosure;

FIG. 7 is a perspective view with parts separated of the articulationmechanism of FIG. 5 according to the present disclosure;

FIG. 8 is an external perspective view with parts assembled of thearticulation mechanism of FIG. 5 according to the present disclosure;

FIG. 9 is a cross-sectional view taken along section line 9-9 in FIG. 5;and

FIG. 10 is a side perspective view of the DLU and a surgical instrumentshown in FIG. 1 prior to attachment of the DLU to the surgicalinstrument;

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the presently disclosed surgical instrument and adisposable loading unit will now be described in detail with referenceto the drawings, in which like reference numerals designate identical orcorresponding elements in each of the several views.

Referring to FIG. 1, surgical instrument 500 includes a handle portion510, a body portion 512, and a disposable loading unit (“DLU”) 16.Handle portion 510 includes a stationary handle 514 and a movable handleor trigger 516. Movable handle 516 is movable in relation to stationaryhandle 514 to advance a control rod 520 which projects from the distalend of body portion 512 (FIG. 10). Handle portion 510 and body portion512 may be constructed in the manner disclosed in a commonly-owned U.S.Pat. No. 6,330,965 entitled “Surgical Stapling Apparatus” the contentsof which are hereby incorporated herein in their entirety by reference.Alternately, other surgical instruments can be used with DLU 16 toperform endoscopic surgical procedures. The surgical instrument 500 alsoincludes an articulation mechanism 400 for articulating a tool assembly17 of the DLU 16.

Referring to FIGS. 1 and 1A, briefly, DLU 16 includes a tool assembly17, a proximal body portion 200 and a mounting assembly 235. Bodyportion 200 has a proximal end adapted to releasably engage the distalend of a surgical instrument 500 (FIG. 10) in the manner to be discussedin detail below. Mounting assembly 235 is pivotally secured to a distalend of body portion 200 and is fixedly secured to a proximal end of toolassembly 17. Pivotal movement of mounting assembly 235 about an axisperpendicular to a longitudinal axis of body portion 200 effectsarticulation of tool assembly 17 between a non-articulated position inwhich the longitudinal axis of tool assembly 17 is aligned with thelongitudinal axis of body portion 200 and an articulated position inwhich the longitudinal axis of tool assembly 17 is disposed at an angleto the longitudinal axis of body portion 200.

Referring also to FIGS. 2-4, tool assembly 17 includes a cartridgeassembly 18 and an anvil assembly 20. Anvil assembly 20 includes ananvil portion 28 having a plurality of staple deforming concavities 30(FIG. 4) and a cover plate 32 secured to a top surface of anvil portion28. Cover plate 32 and anvil portion 28 define a cavity 34 (FIG. 4)therebetween which is dimensioned to receive a distal end of a driveassembly 212 (FIG. 3). Cover plate 32 encloses the distal end of driveassembly 212 to prevent pinching of tissue during actuation of DLU 16. Alongitudinal slot 38 extends through anvil portion 28 to facilitatepassage of a retention flange 40 of drive assembly 212. A cammingsurface 42 formed on anvil portion 28 is positioned to engage a pair ofcam members 40 a supported on retention flange 40 of drive assembly 212to effect approximation of the anvil and cartridge assemblies. A pair ofpivot members 44 formed on anvil portion 28 are positioned within slots46 formed in a cartridge assembly carrier 48 to guide anvil portion 28between its spaced and approximated positions. A pair of stabilizingmembers 50 engage respective shoulders 52 formed on carrier 48 toprevent anvil portion 28 from sliding axially in relation to staplecartridge 54 as camming surface 42 is pivoted about pivot members 44.

Cartridge assembly 18 includes carrier 48 which defines an elongatedsupport channel 56 which is dimensioned and configured to receive staplecartridge 54. Corresponding tabs 58 and slots 60 formed along staplecartridge 54 and elongated support channel 56, respectively, function toretain staple cartridge 54 at a fixed location within support channel56. A pair of support struts 62 formed on staple cartridge 54 ispositioned to rest on side walls of carrier 48 to further stabilizestaple cartridge 54 within support channel 56.

Staple cartridge 54 includes retention slots 64 (FIG. 2) for receiving aplurality of staples or fasteners 66 and pushers 68. A plurality oflaterally spaced apart longitudinal slots 70 extends through staplecartridge 54 to accommodate upstanding cam wedges 72 of an actuationsled 74 (FIG. 2). A central longitudinal slot 76 extends alongsubstantially the length of staple cartridge 54 to facilitate passage ofa knife blade 78 (FIG. 4). During operation of surgical stapler 10,drive assembly 212 abuts actuation sled 74 and pushes actuation sled 74through longitudinal slots 70 of staple cartridge 54 to advance camwedges 72 into sequential contact with pushers 68. Pushers 68 translatevertically along cam wedges 72 within fastener retention slots 64 andurge fasteners 66 from retention slots 64 into staple deforming cavities30 (FIG. 4) of anvil assembly 20.

Referring to FIG. 3, mounting assembly 235 includes an upper mountingportion 236 and a lower mounting portion 238. A centrally located pivotmember 284 extends from upper mounting portion 236 through a respectiveopening 246 a formed in a coupling member 246. Lower mounting portion238 includes a bore 238 e for receiving a pivot member 284 a (FIG. 3F).Pivot member 284 a extends through bore 238 e and second coupling member246. Each of coupling members 246 and 247 include an interlockingproximal portion 246 b, 247 b configured to be received in grooves 290formed in the distal end of an inner housing which is formed from upperand lower housing halves 250 and 252. Coupling members 246, 247 retainmounting assembly 235 and upper and lower housing halves 250 and 252 ina longitudinally fixed position in relation to each other whilepermitting pivotal movement of mounting assembly 235 in relationthereto.

Referring to FIGS. 3A-3C, each coupling members 246, 247 includes acantilevered spring arm 246 c, 247 c which has a distal end 246 dpositioned to engage mounting assembly 235. More specifically, uppermounting portion 236 includes a top surface 236 a which includes arecess 236 b dimensioned to receive distal end 246 d of spring arm 246 cof coupling member 246. Lower mounting portion 238 includes a bottomsurface 238 a having a pair of raised surfaces 238 b which define arecess 238 c which is dimensioned to receive spring arm 247 c ofcoupling member 247. Alternatively, more than one recess may be formedin the upper and lower mounting portions of tool assembly 17, or arecess may be formed on either of the upper and lower mounting portions.

As illustrated in FIGS. 3D-3G, when distal end 246 d of spring arm 246 cof coupling member 246 is positioned in recesses 236 b of upper mountingportion 236, spring arm 246 c retains mounting assembly 235 in anon-articulated position. Spring arm 246 c retains mounting assembly 235in its non-articulated position until a predetermined force sufficientto deflect spring arm 246 c from recess 236 b is applied to effectarticulation of mounting assembly 235 and tool assembly 17. Spring arm247 c is similarly retained in recess 238 c to retain the position ofmounting assembly 235. When the predetermined force is applied to themounting assembly 235 and tool assembly 17, spring arms 246 c, 247 cwill spring outwardly from recesses 236 b and 238 c, as shown in FIGS.3E and 3G, to permit pivotal movement of mounting assembly 235 (and,thus, tool assembly 17) in relation to the distal end of proximal bodyportion 200 of the DLU 16.

As discussed above, spring arms 246 c, 247 c and recesses 236 b and 238c maintain tool assembly 17 in its non-articulated position until apredetermined force has been applied to mounting assembly 235 todisengage spring arms 246 c, 247 c from recesses 236 b and 238 c ofmounting assembly 235. It is envisioned that the spring arms/recessescould be incorporated into any articulating surgical device includingstaplers, graspers (See FIG. 3H), powered sealing devices, e.g., RFsealing devices, etc. Further, although two spring arms/recesses areshown, a single spring arm can be provided. Moreover, the articulatingtool assembly need not for part of a DLU but rather can be supporteddirectly on the distal end of a surgical instrument. For example, themounting assembly can be removably or irremovably secured to the toolassembly and secured directly to the distal end of a surgicalinstrument.

With reference to FIG. 3, upper housing half 250 and lower housing half252 are contained within an outer sleeve 251 of body portion 200. Bodyportion 251 includes a cutout 251 a dimensioned to receive a boss orprojection 250 a formed on upper housing half 250. The positioning ofprojection 250 a within cutout 251 a prevents axial and rotationalmovement of upper and lower housing halves 250 and 252 within outersleeve 251 of body portion 200. In one embodiment, boss 250 a has asubstantially rectangular configuration having a greater axial dimensionthan lateral dimension. The greater axial dimension provides increasedsurface area for preventing rotation of upper and lower housing halves250 and 252 within sleeve 251. A proximal portion 250 b of boss 250 a isramped. Ramped proximal portion 250 b allows sleeve 251 to be slid overboss 250 a as upper and lower housing halves 250 and 252 are positionedwithin sleeve 251. It is envisioned that boss 250 a may assume otherconfigurations, e.g., circular, square, triangular, etc., and stillachieve its intended function. Further, boss 250 a can be repositionedanywhere along upper housing half 250 or, in the alternative, bepositioned on lower housing half 252 or partly on each housing half 250and 252.

The proximal end or insertion tip 193 of upper housing half 250 includesengagement nubs 254 for releasably engaging the distal end of a surgicalinstrument in a bayonet type fashion. Housing halves 250 and 252 definea channel 400 for slidably receiving axial drive assembly 212 therein. Afirst articulation link 256 is dimensioned to be slidably positionedwithin a slot 402 formed between upper and lower housing halves 250 and252. A pair of H-block assemblies 255 are positioned adjacent the distalend of housing portion 200 and adjacent the distal end of axial driveassembly 212 to prevent outward buckling and bulging of drive assembly212 during articulation and firing of surgical stapling apparatus 10.Each H-block assembly 255 includes a flexible body 255 a which includesa proximal end fixedly secured to body portion 200 and a distal endfixedly secured to mounting assembly 235.

A retention member 288 is supported on engagement section 270 of axialdrive assembly 212. Retention member 288 includes a pair of fingers 288a which are releasably positioned within slots or recesses 252 a formedin lower housing half 252. In operation, when SULU 16 is attached to asurgical instrument and axial drive assembly 212 is actuated by applyinga predetermined force to an actuation member 516 of the surgicalinstrument 500 (FIG. 10), axial drive assembly 212 is advanced distallyto move drive assembly 212 and retention member 288 distally. Asretention member 288 is advanced distally, fingers 288 a are forced fromrecesses 252 a to provide an audible and tactile indication that thesurgical instrument has been actuated. Retention member 288 is designedto prevent inadvertent partial actuation of DLU 16, such as duringshipping, by maintaining axial drive assembly 212 at a fixed positionwithin DLU 16 until a predetermined axial force has been applied toaxial drive assembly 212.

Axial drive assembly 212 includes an elongated drive beam 266 includinga distal working head 268 and a proximal engagement section 270. In oneembodiment, drive beam 266 is constructed from multiple stacked sheetsof material. Engagement section 270 includes a pair of resilientengagement fingers 270 a and 270 b which mountingly engage a pair ofcorresponding retention slots formed in drive member 272. Drive member272 includes a proximal porthole 274 configured to receive distal end ofa control rod 520 (FIG. 10) of a surgical instrument when the proximalend of DLU 16 is engaged with the body portion 412 of a surgicalinstrument 500.

With reference to FIGS. 1 and 5-9, an articulation mechanism 400 isshown which includes an articulation knob 402, an articulation spindle404, and a second articulation link 406. The articulation spindle 404provides a mechanical interface between the articulation knob 402 andthe second articulation link 406. The articulation spindle 404 includesa cylindrical member 412 having a first diameter and a flange 414disposed on top of the cylindrical member 412 (See FIG. 7). The flange414 extends laterally from the cylindrical member 412 and has a seconddiameter which is larger than the first diameter of the cylindricalmember 412.

The articulation spindle 404 is rotatably housed within a housing block410 which is integrally formed with the housing of the handle 510. Thehousing block 410 includes a recessed portion 420 having a firstdiameter and a stepped portion 422 having a second diameter. Duringassembly, when the articulation spindle 404 is inserted into the housingblock 410, the cylindrical member 412 and the flange 414 mechanicallyinterface with the recessed portion 420 and stepped portion 422respectively due to corresponding first and second diameters of thesecomponents.

The articulation knob 402 is mounted on top of the articulation spindle404 about a knob interface member 416 which extends upwardly from a topsurface of the flange 414 and is preferably formed integrally therewith.This allows for rotational motion of the articulation knob 402 to betranslated to the rotational motion of the articulation spindle 404. Theinterface member 416 has a polygonal (e.g., rectangular) shapeconfigured for transferring torque exerted by the knob 402 to thearticulation spindle 404. The knob 402 may be integrally formed with thearticulation spindle 404. A cover 405 having an opening for theinterface member 416 to pass therethrough is disposed on top of thearticulation spindle 404 and below the articulation knob 402. The cover405 encloses the components of the articulation mechanism 404 within thehousing block 410. The cover 405 may be secured to the housing block 410via a variety of conventional mechanisms known to those skilled in theart such as screws, rivets, etc.

The second articulation link 406 extends in a longitudinal directionwithin the body portion 512 and includes a second articulation finger424 at a distal end thereof. The articulation finger 424 is configuredto interface with a first articulation finger 426 disposed at a proximalend of the articulation link 256. This allows for translation oflongitudinal movement of the second articulation link 406 to the firstarticulation link 256 which then forces articulation of the toolassembly 17. More specifically, the upper mounting portion 236 includesan articulation pivot member 236 c which extends downwardly from theupper mounting portion 236. The first articulation link 256 includes abore 256 a for receiving the pivot member 236 c. The pivot member 236 cinterconnects the upper and lower mounting portions 236, 238 with thefirst articulation link 256 therebetween as the pivot member 236 cpasses through the bore 256 a. Longitudinal motion of the firstarticulation link 256 forces the upper and lower mounting portions 236and 238 to rotate about the pivot member 284 thereby articulating thetool assembly 17.

The longitudinal motion of the first and second articulation links 256and 406 is imparted via the rotational motion of the articulationspindle 404. The second articulation link 406 mechanically interfaceswith the articulation spindle 404 via a link interface member 418 whichextends downwardly from a bottom surface of the cylindrical member 412of articulation spindle 404. The second articulation link 406 includesan articulation slit 426 which extends laterally across the secondarticulation link 406. The interface member 418 is positioned off centeron the bottom surface of the cylindrical member and is received withinthe slit 426. During rotation of the articulation spindle 404, theinterface member 418 is rotated around the center thereof. Since theslit 426 is dimensioned at its width to substantially fit around theinterface member 418, the interface member 418 only travels in a lateraldirection therein and the longitudinal component of the rotationalmotion of the interface member 418 is translated to the secondarticulation link 406.

The articulation spindle 404 also includes a mechanism for limitingmaximum articulation angle of the tool assembly 17. More specifically,the articulation spindle 404 includes a guide member 430 extendingdownwardly from a bottom surface of the flange 414. The guide member 430is configured to mechanically interface with an arcuately shaped guidechannel 432 which is disposed within a top surface of the steppedportion 422. The guide member 430 moves within the channel 432 andlimits the rotational range of the articulation spindle 404 to thelength of the channel 432.

The articulation mechanism 400 also provides the user with tactilefeedback and means to control the rotation of knob 402 and, hence, thearticulation of tool assembly 17 in predetermined increments. The flange414 includes a series of notches 434 set in an outer circumferentialsurface thereof. The notches 434 are set at a predetermined length apartfrom each other and are configured to interface with a locking mechanism435. The locking mechanism 435 includes a spring loaded plunger 436disposed within a recess 438 in housing block 410, with the plunger 436facing generally perpendicularly with respect to the outercircumferential surface of the flange 414. Another elastic mechanismproviding pressure thereon may be used in lieu of a spring as understoodby those skilled in the art. The plunger 436 due to the spring thereinis pushed against the outer surface of the flange 414 and as thearticulation spindle 404 is rotated, the notches 434 are passed acrossthe plunger 436. When one of the notches 434 is aligned with the plunger436, the plunger 436 is forced into the notch 434 via the spring. Thisallows for indexing the rotational position of the spindle 404 with anarticulation position of the tool assembly 17. The tip of the plunger436 and the notches 434 are preferably formed of complementary shapes(e.g., conical, tapered edges, etc.) to allow for ease of mating anddisengaging upon application of sufficient torque to the articulationspindle 404.

In certain embodiments, the articulation spindle 404 includes fivenotches 434 positioned along the circumferential outer surface of theflange 414. A middle notch 434 coincides with a 0° articulation positionand neighboring notches 434 correspond to ±22.5° and ±45° positionsrespectively for a resulting total articulation angle of 90°. The arclength of the guide channel 432 also corresponds to the maximum desiredarticulation of 90°, such that when the knob 402 is rotated to themaximum articulation positions of ±45°, the guide channel 432 limits themovement of the guide member 430 beyond those points and consequentlylimits rotation of the articulation spindle 404.

When the articulation knob 402 is rotated in either direction, clockwiseor counterclockwise, the articulation spindle 404 initially requires aminimum amount of torque to overcome the locking mechanism 436. Uponreaching the first neighboring notch 434, the plunger 436 is forcedtherein and locks the articulation spindle 404 temporarily in placeproviding tactile feedback to the user. As the articulation spindle 404is rotated, the rotational motion of the interface member 418 istranslated into longitudinal motion of the second articulation link 406via the slit 426 as the interface member 418 travels therein.Longitudinal motion of the articulation link 256 is translated tolongitudinal motion of the articulation pivot member 236 c on mountingassembly 235, which forces the tool assembly 17 to articulate about thepivot member 284. Rotating the articulation spindle 404 to the finalposition of 45°, locks the tool assembly 17 in place due to the guidemember 430 of the articulating spindle 404 encountering the end of theguide channel 432 and the plunger 436 interfacing with the furthestnotch 434. To unlock the tool assembly 17, the knob 402 is turned in theopposite direction, traversing through other notches 434 and the neutralaxial plane (e.g., 0°) of the middle notch 434. The rotational range ofthe knob 402 is ±95° which corresponds with articulating the toolassembly 17 between ±45° positions.

Those skilled in the art will appreciate that the articulation spindle404 may include any number of notches 434 disposed at various intervalsdepending on the desired articulation angles and/or positions. It isfurther to be understood that the articulation angles and maximumrotation ranges disclosed with respect to the articulation mechanism 400are illustrative.

Referring to FIG. 9, shows a cross-sectional view of a sensing mechanism450 operatively associated with the articulation mechanism 400 andpositioned within the housing block 410. The sensing mechanism 450includes a cap sensor 444 having a nub portion 442 configured to bereceived within a slot 440 of the articulation spindle 404. The capsensor 444 is adapted to sense the type of a disposable loading unit 16engaged with the body portion 512. In particular, the cap sensor 444 isconfigured to interface with the articulation spindle 404 and preventarticulation thereof if the nub portion 442 is recessed within the slot440. The articulating disposable loading unit 16 has an extendedinsertion tip 193 (FIG. 1A). When the articulating DLU is inserted intothe distal end of body portion 512 of stapling apparatus 10, insertiontip 193 moves proximally into engagement with cap sensor 444 to forcethe cap sensor 444 and nub portion 442 proximally and out of the slot440. With nub portion 442 positioned outside the slot 444, thearticulation spindle 404 is free to move rotatably to effectarticulation of stapling apparatus 10. A non-articulating disposableloading unit does not have an extended insertion tip. As such, when anon-articulating disposable loading unit is inserted, cap sensor 444 isnot retracted proximally a sufficient distance to move the nub portion442 from slot 444. Thus, articulation spindle 404 is prevented frommoving rotatably by nub portion 442 of the cap sensor 444 which ispositioned in slot 444 and the articulation spindle 404 is locked in itsneutral position. Another type of sensing mechanism is described in acommonly-owned U.S. Pat. No. 5,865,361 entitled “Surgical StaplingApparatus” the contents of which are hereby incorporated herein in theirentirety by reference.

It will be understood that various modifications may be made to theembodiments disclosed herein. For example, the DLU may be configured toreceive an insertion tip of surgical instrument in contrast to thatdisclosed. Therefore, the above description should not be construed aslimiting, but merely as exemplifications of preferred embodiments. Thoseskilled in the art will envision other modifications within the scopeand spirit of the claims appended hereto.

1-29. (canceled)
 30. A surgical instrument, comprising: a handleportion; a body portion extending distally from the handle portion anddefining a first longitudinal axis; a tool assembly defining a secondlongitudinal axis and including at least one recess therein, the toolassembly being disposed at a distal end of the body portion and beingmovable from a first position in which the second longitudinal axis issubstantially aligned with the first longitudinal axis to at least asecond position in which the second longitudinal axis is disposed at anangle to the first longitudinal axis; and an arm disposed in the recessof the tool assembly to releasably retain the tool assembly in the firstposition until a predetermined force sufficient to deflect the armoutwardly is applied to the tool assembly to articulate the toolassembly, wherein the tool assembly is releasably retained in the firstposition when the arm is disposed within the recess, and wherein thetool assembly is free to move toward the second position when the armhas been disengaged from the recess; and an articulation mechanismincluding a spindle and an articulation link for articulating the toolassembly, wherein the articulation mechanism includes a plunger biasedto engage the spindle.
 31. The surgical instrument according to claim30, wherein the arm is attached to a coupling member secured to aportion of the body portion.
 32. The surgical instrument according toclaim 30, wherein an articulation knob is operatively coupled to thespindle.
 33. The surgical instrument according to claim 32, wherein thespindle has a cylindrical member operatively coupled to the articulationlink, wherein rotational motion of the articulation knob is translatedinto axial motion of the articulation link thereby articulating the toolassembly.
 34. The surgical instrument according to claim 30, wherein thearticulation mechanism further includes a housing block configured toreceive the spindle, the spindle being coupled to an articulation knobso as to rotate therewith.
 35. The surgical instrument according toclaim 34, wherein the housing block and the spindle are adapted to limita rotational range of the articulation spindle.
 36. The surgicalinstrument according to claim 30, wherein the spindle defines aplurality of notches, the plurality of notches configured tomechanically interface with the plunger.
 37. The surgical instrumentaccording to claim 36, wherein each of the plurality of notches sets apredetermined position of the tool assembly.
 38. The surgical instrumentaccording to claim 37, wherein at least one of the notches correspondswith the first position of the tool assembly.
 39. The surgicalinstrument according to claim 30, wherein the tool assembly includes acartridge assembly and an anvil assembly.
 40. The surgical instrumentaccording to claim 30, wherein a proximal end of the tool assemblyincludes a mounting portion.
 41. The surgical instrument according toclaim 40, wherein the recess is formed in the mounting portion.
 42. Thesurgical instrument according to claim 30, wherein the an arm springsoutwardly from the recess upon application of the predetermined force.43. The surgical instrument according to claim 30, wherein the recess isdefined at least in part by a pair of sloped walls.